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Ruby implementation for GMercatorProjection
# This is a port of the javascript code found in the following link
#http://groups.google.com/group/Google-Maps-API/browse_thread/thread/a45947d72c27cc73
class Mercator
#offset is defined at zoom level 21 which means that this Mercator is valid for 21 zoom levels
OFFSET = 268435456
RADIUS = OFFSET / Math::PI
def self.lng_to_x(lng, zoom)
(OFFSET + RADIUS * lng * Math::PI / 180).to_i >> (21 - zoom)
end
def self.lat_to_y(lat, zoom)
(OFFSET-RADIUS*Math.log((1+Math.sin(lat*Math::PI/180))/(1-Math.sin(lat*Math::PI/180)))/2).to_i >> (21 - zoom)
end
def self.x_to_lng(x, zoom)
(((x<<(21 - zoom))-OFFSET)/RADIUS)*180/Math::PI
end
def self.y_to_lat(y, zoom)
(Math::PI/2-2*Math.atan(Math.exp(((y<< (21 - zoom))-OFFSET)/RADIUS)))*180/Math::PI
end
end
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